Posted by: spinalfitness.com () on Thu Sep 4 17:28:43 2003

Fulcrum/lever hitting with bat

A fulcrum system would for instance in the lower back consist of two spinal vertebrae. The bat essentially when contacting the ball would form a effective resistance lever arm back to the fulcrum. The muscles used to move and stabilize the bat that crossed the lower back fulcrum would form the effective effort arm back to the fulcrum.

In the standing position the effective effort and resistance arm would be used to calculate equilibrium of torque. Or given the resistance force of the ball how much muscle effort is needed to stabilize the resistance.

The force of resistance and force would create a resultant force on the superior vertebra. I am assuming that in addition to the resistance of the ball we would also be experiencing resistance of the upper trunk in gravity and the bat in gravity. The pull of the muscle of effort in the abdomen (rectus, oblique) would be pulling downward towards pelvis into the negative y-axis. It appears that resolving the pulls of resistance with the pulls of effort we would get a resultant force into the negative y-axis.

This means that due to principle of equilibrium of translation that the superior vertbra would translate in a downward direction. This means that the inferior vertebra would supply the stabilizing force or in lever language the true effort arm and would stabilize the resultant force. Due to needing to saftisfy equilibrium of torque and equilibrium of translation which are both present in all levers such as this that any lever system would have to include two spinal vertbrae.